1. Field of the Invention
The present invention relates to an engine starting device and an engine starting method for an automatic idle-stop system for performing an engine idle stop when a predetermined idle-stop condition is satisfied and restarting an engine when a restart condition is thereafter satisfied.
2. Description of the Related Art
For the purposes of improving fuel efficiency and reducing an environmental load of automobiles, there have heretofore been developed automatic idle-stop systems for automatically performing an idle stop with the satisfaction of a predetermined condition.
However, when a restart request for an engine is generated while the engine is rotating backward, and the engine is started by the starter motor, the starter motor causes the engine, which is rotating backward, to rotate forward and an excessively large load acts on the starter motor. In view of this, there is known a configuration for detecting, by backward rotation detection means for detecting whether or not the engine is rotating backward, a backward rotation when the engine is rotating backward for some reason, inhibiting drive of the starter motor, and preventing the starter motor and a power transmission mechanism thereof from being damaged (for example, refer to Japanese Patent Application Laid-open No. 2005-140030).
However, the conventional technology has the following problem.
As described above, the invention according to Japanese Patent Application Laid-open No. 2005-140030 includes the backward rotation detection means for detecting whether or not the engine is rotating backward, and the means for inhibiting, when a backward rotation is detected, the motor from rotating, thereby preventing, when the engine is rotating backward, the motor from rotating. However, with the invention according to Japanese Patent Application Laid-open No. 2005-140030, it is necessary to provide the backward rotation detection means for detecting the backward rotation of the engine, and there thus poses a problem in that the device becomes complex and the cost increases.